The present invention relates to a hydraulic control assembly. In particular, but not exclusively, the present invention relates to a hydraulic control assembly for controlling the operation of one or more downhole tools such as, for example, a circulation valve, a bore isolation unit, a gun system and/or any desired valve assembly.
A variety of tools and valves are used downhole in an oil and/or gas well, which tools may, for example, be operated by annulus pressure, tubing pressure or control lines. In particular, a number of downhole tools are required in a borehole of an oil and/or gas well for drilling the borehole and throughout the production period of the well. Often a number of different tools are disposed within the borehole simultaneously, making individual control and/or operation of the tools complex. Furthermore, it may be difficult to ensure that a selected tool is in an activater or reactivated configuration as required.
Also, most downhole tools have internal mechanisms which cycle the tool, or operate them in a particular fashion. These mechanisms take the tool function in a unique and limited fashion. Furthermore, the tools become complex and cumbersome, with built-in weaknesses created by compromises between operating conditions, tool function and size.
It is amongst the objects of the present invention to obviate or mitigate at least one of the foregoing problems.
According to a first aspect of the present invention, there is provided a hydraulic control assembly for controlling the operation of a downhole tool, the assembly being for disposition in a borehole of a well and comprising:
a tubular member having a substantially axially extending chamber, the chamber having a tool control fluid inlet and outlet, the inlet for injecting a tool control fluid into the chamber, and the outlet for fluidly coupling to the downhole tool to control the operation of the tool; and
flow control means for selectively allowing flow of the tool control fluid from the tool control fluid inlet to the tool control fluid outlet.
In this fashion, the present invention may allow a downhole tool coupled to the hydraulic control assembly to be selectively activated deactivated and/or maintained in an activated or deactivated configuration, by selectively allowing flow of the tool control fluid through the chamber of the tubular member.
Conveniently, the tubular member is a casing, lining or well tubing for running-in to the borehole. Preferably, the chamber is formed in a wall of the tubular member. Preferably also, a plurality of axially extending chambers are provided disposed spaced around a circumference of the wall of the tubular member. Alternatively, the chamber may be formed in a housing adapted to be coupled to a length of casing, lining or well tubing. The housing may be coupled to an outer or inner surface of the casing, lining or well tubing.
The flow control means may comprise a movable, substantially cylindrical shuttle valve disposed in the chamber, the shuttle valve comprising at least two radially extending seals for sealing the shuttle valve in the chamber and isolating the tool control fluid outlet from the tool control fluid inlet. The shuttle valve may be axially movable to selectively allow flow of the tool control fluid from the tool control fluid inlet to the tool control fluid outlet.
Conveniently, the flow control means further comprises a gear rod for axially moving the shuttle valve to allow flow of the tool control fluid. The gear rod may comprise ratchet teeth formed on an other surface thereof, and may co-operate with an axially movable mounting cage disposed in the chamber and having a ratchet arm for engaging the teeth of the gear rod. Thus the present invention may allow the shuttle valve to be axially moved to allow flow of control fluid to the downhole tool, by axially moving the gear rod in the mounting cage. Movement of the gear rod is achieved by an interaction between the ratchet teeth of the gear rod and the ratchet arm of the mounting cage.
Preferably, the mounting cage is substantially tubular. The mounting cage may include an upper piston disposed in a cylinder. Preferably, the flow control means further comprises a first fluid inlet fluidly coupled to the cylinder and a second fluid inlet fluidly coupled to the chamber. Thus by selectively injecting fluid into the cylinder and withdrawing fluid from the second fluid inlet, the cage may be moved axially towards the shuttle valve carrying the gear rod therewith.
The flow control means may further comprise a collect disposed in the chamber, the collet having radially extending ratchet arms for engaging the ratchet teeth of the gear rod. Thus, by injecting fluid via the second fluid inlet, and withdrawing fluid via the first fluid inlet, the cage may be moved axially away from the shuttle valve, with the gear rod retained by the collet. The gear rod may therefore be axially moved towards the shuttle valve in step wise fashion.
According to a second aspect of the present invention, there is provided a hydraulic control assembly for controlling the operation of a downhole tool, the assembly being adapted to be located in a borehole of a well and comprising:
a moveable piston;
a tubular member having a substantially axially extending chamber, the chamber having at least two tool control fluid ports for allowing tool control fluid to flow through the chamber; and
flow control means for selectively allowing flow of tool control fluid through one of said ports to the chamber and from the chamber through the other one of said ports to the tool, to control operation of the tool, the flow control means being selectively activated, to allow tool control fluid flow to the tool, by the moveable piston.
Advantageously, this provides a hydraulic control assembly wherein a moveable piston may be moved to cause a flow control means to allow flow of tool control fluid to a downhole tool couple to the hydraulic control assembly. Preferably, flow of tool control fluid to the chamber occurs simultaneously with flow of tool control fluid from the chamber.
The piston may carry an operating finger for engaging the flow control means, to selectively activate the flow control means to in turn allow tool control fluid flow to the tool. Conveniently, the assembly includes a ratchet assembly for restraining the piston. The ratchet assembly may be a ball race ratchet including a ball race track formed in an outer surface of the piston and a ball adapted to engage in the track. The track may define a number of axially spaced rest positions for the ball, with a number of first rest positions for restraining the piston from further axial movement away from the tubular member, and a number of second rest positions, spaced axially from the first rest positions, to restrain the piston from further axial movement towards the tubular member. The rest positions may be formed in the track to define a continuous track for ball to follow. The first and second rest positions may be aligned around the circumference of the piston, and the track may define axial portions extending between the first and second rest positions, and angled track portions connecting adjacent pairs of first and second rest positions.
In this fashion, when the piston is moved axially towards and away form the tubular member, the piston is rotated by an interaction between the ball and the track. The piston may be moved axially by variation of a fluid pressure applied to the piston. This may be achieved by coupling a control line to the piston, or by varying the pressure internally within the hydraulic control assembly, or externally, in an annular defined between the assembly and a borehole wall. Conveniently, the ball is coupled to a casing or other tubing in which the hydraulic control assembly is located separately.
Preferably, the assembly includes two chambers and corresponding flow control means for controlling the operation of two downhole tools, or for separately controlling different aspects or operations of a single tool, for example the opening and closing of a valve. Alternatively, the assembly may include three or more chambers and corresponding flow control means. The piston may include operating fingers arranged so as to selectively activate a desired one or more flow control means in a desired order. Advantageously, the hydraulic control assembly is particularly adapted to the operating conditions required for manipulation of particular downhole tools, and these tools can be activated and/or deactivated by, for example, simple pressure signals in fluid in a borehole in which the assembly is located. Further advantageously, this allows each downhole tool required to perform a specific task to be very simple in structure and operation.
Preferably, the assembly comprises four tool control fluid ports, that is two fluid supply ports for flow of tool control fluid to the tool, and two fluid return ports for return or xe2x80x9cbleedng offxe2x80x9d of tool control fluid from the tool. The downhole tool may be coupled to the hydraulic control assembly in a closed loop with respect to the fluid in the chamber. Advantageously, this allows the downhole tool to be simply and effectively operated solely on the basis of opposing hydraulics, with operation of the tool in one fashion achieved by flow of control fluid to the tool from the chamber, and operation of the tool in the opposite or an alternative fashion by flow of control fluid from the tool into the chamber through the fluid return ports.
The tool control fluid ports may be spaced axially along the chamber and may be selectively isolated from one another by the flow control means. Each of the two fluid supply flow ports and the two fluid return flow ports may be mutually axially spaced.
The flow control means is preferably located in the chamber. The chamber may include seals for sealing the flow control means in the chamber to selectively isolate the tool control fluid ports. A pair of seals may be provided in the chamber axially straddling one of each of the two fluid supply flow ports and the two fluid return flow ports. In particular, seals may be provided axially straddling the fluid supply flow port, through which fluid flows from the chamber to the tool, and the fluid return flow port, through which fluid returns from the tool to the chamber.
The flow control means may be movable between deactivated and activated positions, where the means respectively prevents and allows tool control fluid flow to and from the tool to control operation of the tool. The assembly may further comprise biassing means for biassing the flow control means towards the deactivated position. The piston may act against the biassing means to move the flow control means to the activated position. In the deactivated position, the flow control means may isolate the tool control fluid ports to prevent communication between the ports to the tool. In the activated position, the flow control means may be moved to a position where the flow of tool control fluid is permitted between the tool control fluid ports and to the tool.
The flow control means may comprise an axially moveable plunger. The plunger may be spring biassed and may have an end adapted to be engaged by the moveable piston. Alternatively, the plunger may be moveable by application of fluid pressure. The plunger may be substantially cylindrical and may include a hollow portion defining a fluid conduit within the cylinder for selectively allowing fluid flow between the tool control fluid ports. Preferably, two such hollow portions are provided, one for each of the two fluid supply flow ports and fluid return flow ports. The piston in the region of the hollow portion may include apertures in a wall thereof, to allow fluid to enter the piston and into the fluid conduit.
Accordingly it will be understood that when the piston is moved between the deactivated and activated positions, the location of the tool control fluid ports and the seals with respect to the hollow portions selectively allows fluid communication between respective ones of the ports when the piston is moved axially to the activated position.
The plunger be adapted to be engaged by the moveable piston, and the plunger may be biassed by a biassing spring against the action of the movable piston.
The tubular member may include vent ports in the chamber provided for venting fluid from the chamber when the flow control means is moved by the moveable piston.
The hydraulic control assembly may further comprise a tool control fluid reservoir coupled to the chamber. The reservoir may be provided integrally with the tubular member, or may be provided externally of the tubular member. The reservoir may comprise a cylinder having an activating piston for ejecting fluid from the reservoir. The piston may be moved to eject fluid from the reservoir by application of fluid pressure. Fluid pressure may be applied by either control line, internal or external pressure acting on the hydraulic control assembly. The reservoir may be coupled to the chamber through one of the tool control fluid ports by a coupling fluid line. The reservoir may include a valve to prevent fluid return from the chamber.
Conveniently, the hydraulic control assembly includes fluid expansion vents to allow for expansion of the tool control fluid downhole. The fluid expansion vents may include cylinders having biassed pistons, the cylinders adapted to accommodate any expansion of the tool control fluid. Such may occur, in particular, due to the increased pressures and temperatures experienced downhole. The expansion vents are conveniently coupled to fluid flow lines of the hydraulic control assembly.
The hydraulic control assembly may further comprise restriction orifices provided in lines extending from the tool control fluid ports to prevent surge washing damage. Preferably, the restriction orifices are located in the lines through which fluid flows from the chamber to the tool and/or from the tool to the chamber.
According to a third aspect of the present invention, there is provided a method for controlling the operation of a fluidly activated downhole tool for disposition in a borehole of a well, the method comprising the steps of:
disposing the fluidly activated tool in the borehole;
fluidly coupling first and second control fluid supply conduits to the downhole tool in a fluidly closed-loop configuration; and
Injecting control fluid into the downhole tool via a selected one of said first and second control fluid supply conduits, whilst simultaneously bleeding fluid out of the downhole tool via the other of said first and second control fluid supply conduits, to selectively activate the downhole tool.
Preferably, the method further comprises the step of measuring one of both of the volume of control fluid injected into the downhole tool or bled from the tool to allows accurate determination of an operating status of the downhole tool.